2 * This contains encryption functions for per-file encryption.
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
7 * Written by Michael Halcrow, 2014.
9 * Filename encryption additions
10 * Uday Savagaonkar, 2014
11 * Encryption policy handling additions
12 * Ildar Muslukhov, 2014
13 * Add fscrypt_pullback_bio_page()
16 * This has not yet undergone a rigorous security audit.
18 * The usage of AES-XTS should conform to recommendations in NIST
19 * Special Publication 800-38E and IEEE P1619/D16.
22 #include <linux/pagemap.h>
23 #include <linux/mempool.h>
24 #include <linux/module.h>
25 #include <linux/scatterlist.h>
26 #include <linux/ratelimit.h>
27 #include <linux/dcache.h>
28 #include <linux/namei.h>
29 #include "fscrypt_private.h"
31 static unsigned int num_prealloc_crypto_pages = 32;
32 static unsigned int num_prealloc_crypto_ctxs = 128;
34 module_param(num_prealloc_crypto_pages, uint, 0444);
35 MODULE_PARM_DESC(num_prealloc_crypto_pages,
36 "Number of crypto pages to preallocate");
37 module_param(num_prealloc_crypto_ctxs, uint, 0444);
38 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
39 "Number of crypto contexts to preallocate");
41 static mempool_t *fscrypt_bounce_page_pool = NULL;
43 static LIST_HEAD(fscrypt_free_ctxs);
44 static DEFINE_SPINLOCK(fscrypt_ctx_lock);
46 struct workqueue_struct *fscrypt_read_workqueue;
47 static DEFINE_MUTEX(fscrypt_init_mutex);
49 static struct kmem_cache *fscrypt_ctx_cachep;
50 struct kmem_cache *fscrypt_info_cachep;
53 * fscrypt_release_ctx() - Releases an encryption context
54 * @ctx: The encryption context to release.
56 * If the encryption context was allocated from the pre-allocated pool, returns
57 * it to that pool. Else, frees it.
59 * If there's a bounce page in the context, this frees that.
61 void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
65 if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
66 mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
67 ctx->w.bounce_page = NULL;
69 ctx->w.control_page = NULL;
70 if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
71 kmem_cache_free(fscrypt_ctx_cachep, ctx);
73 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
74 list_add(&ctx->free_list, &fscrypt_free_ctxs);
75 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
78 EXPORT_SYMBOL(fscrypt_release_ctx);
81 * fscrypt_get_ctx() - Gets an encryption context
82 * @inode: The inode for which we are doing the crypto
83 * @gfp_flags: The gfp flag for memory allocation
85 * Allocates and initializes an encryption context.
87 * Return: An allocated and initialized encryption context on success; error
88 * value or NULL otherwise.
90 struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
92 struct fscrypt_ctx *ctx = NULL;
93 struct fscrypt_info *ci = inode->i_crypt_info;
97 return ERR_PTR(-ENOKEY);
100 * We first try getting the ctx from a free list because in
101 * the common case the ctx will have an allocated and
102 * initialized crypto tfm, so it's probably a worthwhile
103 * optimization. For the bounce page, we first try getting it
104 * from the kernel allocator because that's just about as fast
105 * as getting it from a list and because a cache of free pages
106 * should generally be a "last resort" option for a filesystem
107 * to be able to do its job.
109 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
110 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
111 struct fscrypt_ctx, free_list);
113 list_del(&ctx->free_list);
114 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
116 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
118 return ERR_PTR(-ENOMEM);
119 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
121 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
123 ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
126 EXPORT_SYMBOL(fscrypt_get_ctx);
129 * page_crypt_complete() - completion callback for page crypto
130 * @req: The asynchronous cipher request context
131 * @res: The result of the cipher operation
133 static void page_crypt_complete(struct crypto_async_request *req, int res)
135 struct fscrypt_completion_result *ecr = req->data;
137 if (res == -EINPROGRESS)
140 complete(&ecr->completion);
143 int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
144 u64 lblk_num, struct page *src_page,
145 struct page *dest_page, unsigned int len,
146 unsigned int offs, gfp_t gfp_flags)
150 u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
152 struct skcipher_request *req = NULL;
153 DECLARE_FS_COMPLETION_RESULT(ecr);
154 struct scatterlist dst, src;
155 struct fscrypt_info *ci = inode->i_crypt_info;
156 struct crypto_skcipher *tfm = ci->ci_ctfm;
161 req = skcipher_request_alloc(tfm, gfp_flags);
163 printk_ratelimited(KERN_ERR
164 "%s: crypto_request_alloc() failed\n",
169 skcipher_request_set_callback(
170 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
171 page_crypt_complete, &ecr);
173 BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
174 xts_tweak.index = cpu_to_le64(lblk_num);
175 memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));
177 sg_init_table(&dst, 1);
178 sg_set_page(&dst, dest_page, len, offs);
179 sg_init_table(&src, 1);
180 sg_set_page(&src, src_page, len, offs);
181 skcipher_request_set_crypt(req, &src, &dst, len, &xts_tweak);
182 if (rw == FS_DECRYPT)
183 res = crypto_skcipher_decrypt(req);
185 res = crypto_skcipher_encrypt(req);
186 if (res == -EINPROGRESS || res == -EBUSY) {
187 BUG_ON(req->base.data != &ecr);
188 wait_for_completion(&ecr.completion);
191 skcipher_request_free(req);
193 printk_ratelimited(KERN_ERR
194 "%s: crypto_skcipher_encrypt() returned %d\n",
201 struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
204 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
205 if (ctx->w.bounce_page == NULL)
206 return ERR_PTR(-ENOMEM);
207 ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
208 return ctx->w.bounce_page;
212 * fscypt_encrypt_page() - Encrypts a page
213 * @inode: The inode for which the encryption should take place
214 * @page: The page to encrypt. Must be locked for bounce-page
216 * @len: Length of data to encrypt in @page and encrypted
217 * data in returned page.
218 * @offs: Offset of data within @page and returned
219 * page holding encrypted data.
220 * @lblk_num: Logical block number. This must be unique for multiple
221 * calls with same inode, except when overwriting
222 * previously written data.
223 * @gfp_flags: The gfp flag for memory allocation
225 * Encrypts @page using the ctx encryption context. Performs encryption
226 * either in-place or into a newly allocated bounce page.
227 * Called on the page write path.
229 * Bounce page allocation is the default.
230 * In this case, the contents of @page are encrypted and stored in an
231 * allocated bounce page. @page has to be locked and the caller must call
232 * fscrypt_restore_control_page() on the returned ciphertext page to
233 * release the bounce buffer and the encryption context.
235 * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
236 * fscrypt_operations. Here, the input-page is returned with its content
239 * Return: A page with the encrypted content on success. Else, an
240 * error value or NULL.
242 struct page *fscrypt_encrypt_page(const struct inode *inode,
246 u64 lblk_num, gfp_t gfp_flags)
249 struct fscrypt_ctx *ctx;
250 struct page *ciphertext_page = page;
253 BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
255 if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
256 /* with inplace-encryption we just encrypt the page */
257 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
258 ciphertext_page, len, offs,
263 return ciphertext_page;
266 BUG_ON(!PageLocked(page));
268 ctx = fscrypt_get_ctx(inode, gfp_flags);
270 return (struct page *)ctx;
272 /* The encryption operation will require a bounce page. */
273 ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags);
274 if (IS_ERR(ciphertext_page))
277 ctx->w.control_page = page;
278 err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
279 page, ciphertext_page, len, offs,
282 ciphertext_page = ERR_PTR(err);
285 SetPagePrivate(ciphertext_page);
286 set_page_private(ciphertext_page, (unsigned long)ctx);
287 lock_page(ciphertext_page);
288 return ciphertext_page;
291 fscrypt_release_ctx(ctx);
292 return ciphertext_page;
294 EXPORT_SYMBOL(fscrypt_encrypt_page);
297 * fscrypt_decrypt_page() - Decrypts a page in-place
298 * @inode: The corresponding inode for the page to decrypt.
299 * @page: The page to decrypt. Must be locked in case
300 * it is a writeback page (FS_CFLG_OWN_PAGES unset).
301 * @len: Number of bytes in @page to be decrypted.
302 * @offs: Start of data in @page.
303 * @lblk_num: Logical block number.
305 * Decrypts page in-place using the ctx encryption context.
307 * Called from the read completion callback.
309 * Return: Zero on success, non-zero otherwise.
311 int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
312 unsigned int len, unsigned int offs, u64 lblk_num)
314 if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
315 BUG_ON(!PageLocked(page));
317 return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
318 len, offs, GFP_NOFS);
320 EXPORT_SYMBOL(fscrypt_decrypt_page);
323 * Validate dentries for encrypted directories to make sure we aren't
324 * potentially caching stale data after a key has been added or
327 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
330 int dir_has_key, cached_with_key;
332 if (flags & LOOKUP_RCU)
335 dir = dget_parent(dentry);
336 if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
341 /* this should eventually be an flag in d_flags */
342 spin_lock(&dentry->d_lock);
343 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
344 spin_unlock(&dentry->d_lock);
345 dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
349 * If the dentry was cached without the key, and it is a
350 * negative dentry, it might be a valid name. We can't check
351 * if the key has since been made available due to locking
352 * reasons, so we fail the validation so ext4_lookup() can do
355 * We also fail the validation if the dentry was created with
356 * the key present, but we no longer have the key, or vice versa.
358 if ((!cached_with_key && d_is_negative(dentry)) ||
359 (!cached_with_key && dir_has_key) ||
360 (cached_with_key && !dir_has_key))
365 const struct dentry_operations fscrypt_d_ops = {
366 .d_revalidate = fscrypt_d_revalidate,
368 EXPORT_SYMBOL(fscrypt_d_ops);
370 void fscrypt_restore_control_page(struct page *page)
372 struct fscrypt_ctx *ctx;
374 ctx = (struct fscrypt_ctx *)page_private(page);
375 set_page_private(page, (unsigned long)NULL);
376 ClearPagePrivate(page);
378 fscrypt_release_ctx(ctx);
380 EXPORT_SYMBOL(fscrypt_restore_control_page);
382 static void fscrypt_destroy(void)
384 struct fscrypt_ctx *pos, *n;
386 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
387 kmem_cache_free(fscrypt_ctx_cachep, pos);
388 INIT_LIST_HEAD(&fscrypt_free_ctxs);
389 mempool_destroy(fscrypt_bounce_page_pool);
390 fscrypt_bounce_page_pool = NULL;
394 * fscrypt_initialize() - allocate major buffers for fs encryption.
395 * @cop_flags: fscrypt operations flags
397 * We only call this when we start accessing encrypted files, since it
398 * results in memory getting allocated that wouldn't otherwise be used.
400 * Return: Zero on success, non-zero otherwise.
402 int fscrypt_initialize(unsigned int cop_flags)
404 int i, res = -ENOMEM;
407 * No need to allocate a bounce page pool if there already is one or
408 * this FS won't use it.
410 if (cop_flags & FS_CFLG_OWN_PAGES || fscrypt_bounce_page_pool)
413 mutex_lock(&fscrypt_init_mutex);
414 if (fscrypt_bounce_page_pool)
415 goto already_initialized;
417 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
418 struct fscrypt_ctx *ctx;
420 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
423 list_add(&ctx->free_list, &fscrypt_free_ctxs);
426 fscrypt_bounce_page_pool =
427 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
428 if (!fscrypt_bounce_page_pool)
432 mutex_unlock(&fscrypt_init_mutex);
436 mutex_unlock(&fscrypt_init_mutex);
441 * fscrypt_init() - Set up for fs encryption.
443 static int __init fscrypt_init(void)
445 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
447 if (!fscrypt_read_workqueue)
450 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
451 if (!fscrypt_ctx_cachep)
452 goto fail_free_queue;
454 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
455 if (!fscrypt_info_cachep)
461 kmem_cache_destroy(fscrypt_ctx_cachep);
463 destroy_workqueue(fscrypt_read_workqueue);
467 module_init(fscrypt_init)
470 * fscrypt_exit() - Shutdown the fs encryption system
472 static void __exit fscrypt_exit(void)
476 if (fscrypt_read_workqueue)
477 destroy_workqueue(fscrypt_read_workqueue);
478 kmem_cache_destroy(fscrypt_ctx_cachep);
479 kmem_cache_destroy(fscrypt_info_cachep);
481 module_exit(fscrypt_exit);
483 MODULE_LICENSE("GPL");